Mold reciprocating mechanism for continuous casting machines

ABSTRACT

A mold reciprocating mechanism having a cylindrical piston open at both ends and containing a pour-through mold cartridge therein. A cylinder encircles the central part of the piston and is provided with pressure fluid to reciprocate the piston, and hence the mold cartridge. The piston can rotate axially in the cylinder to reduce axial misalignment of a strand, and the mold cartridge can move slightly from side to side in the piston to reduce side to side strand misalignment. The cylinder is leveled on a frame by adjusting screws, and this also levels the mold and properly orients the axis of reciprocation. Flexible hoses conduct coolant to the piston.

United States Patent [72] Inventors Tibor Miklos Vertesi Whitby, Ontario; Bruce Allan Phillips, Ajax, Ontario, Canada [21] Appl. No. 767,616 [22] Filed Oct. 15,1968 [45] Patented Feb. 23, 1971 [73] Assignee Gamma Engineering Limited Whitby, Ontario, Canada [54] MOLD RECIPROCATING MECHANISM FOR CONTINUOUS CASTING MACHINES 11 Claims, 7 Drawing Figs.

[52] US. Cl. 164/154, 164/83, 164/157, 164/260 [51] Int. Cl. 822d 17/32 [50] Field of Search 164/4, 83, 154, 260, 282, 283,157

[5 6] References Cited UNITED STATES PATENTS 2,135,183 11/1938 .Iunghans 164/83 2,709,842 6/1955 Findlay l64/260X 7 3,025,579 3/1962 Littlewood 164/ 154 3,040,397 6/l962 Haussner et al. 164/154 3,338,297 8/1967 Foldessy l64/282X FOREIGN PATENTS 1,359,752 3/1964 France 164/282 965,884 8/1964 Great Britain 164/282 OTHER REFERENCES Scientific American Vol. 209, No. 6, December 1963. pp. 75-88. Tl.55.

Primary Examiner-J. Spencer Overholser Assistant ExaminerR. Spencer Annear Attorney-Rogers, Bereskin & Parr ABSTRACT: A mold reciprocating mechanism having a cylindrical piston open at both ends and containing a pour-through mold cartridge therein. A cylinder encircles the central part of the piston and is provided with pressure flnid to reciprocate the piston, and hence the mold cartridge. The piston can rotate axially in the cylinder to reduce axial misalignment of a strand, and the mold cartridge can move slightly from side to side in the piston to reduce side to side strand misalignment. The cylinder is leveled on a frame by adjusting screws, and this also levels the mold and properly orients the axis of reciprocation. Flexible hoses conduct coolant to the piston.

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INVIiN'IURS TIBOR M. VERTESI BY BRUCE Af PHILLIPS MOLD RECIPROCATING MECHANISM FOR CONTINUOUS CASTING MACHINES This invention relates to continuous casting machines for casting metal. More particularly, it relates to a'reciprocating mold mechanism for such machines, and to a control system and a roller apron which may be used with the reciprocating mold mechanism.

Continuous strands of cast metal such as steel are produced by pouring the metal in a molten state through the top of a flow-through casting mold and withdrawing the metal continuously from an opening in the bottom of the mold as an elongated strand of square or rectangular dross section. In order to withdraw the metal in this manner, the mold is usually placed in an elevated position and located above the mold is a ladle transporting the molten metal to the apparatus, together with a tundish to receive the metal from the ladle and feed it into the mold or a plurality of molds.

To begin the continuous casting operation, the bottom opening of the mold, from which the metal is to be continuously withdrawn, is initially plugged by'a head attached to the end of a starting device moving along a guideway. The molten metal in the mold solidifies about the head which is then withdrawn from the bottom opening of the mold followed by a continuous strand of the metal. The metal progressively solidifies as it emerges and moves away from the mold. Vibrating apparatus is required to help prevent the molten metal from adhering to the sides of the mold during its sojourn within the mold and to work inlubricant between the metal and the mold. It is such vibrating apparatus with which the present invention is primarily concerned.

In the past, molds used for continuous casting were usually mounted on springs in a large frame and were connected to a special oscillating mechanism. It was necessary carefully to level both the-frame and the mold\in the frame, and also to align both relative to each other and relative to a roller apron located therebelow, to prevent stresses in the emerging cast strand. In addition, it was difficult 'to obtain truly vertical linear reciprocating motion of the mold. Furthermore, the prior art mechanisms were typically extremely heavy and therefore required massive support structures.

Accordingly, it is an object of the present invention to provide a mold reciprocating mechanism of reduced cost that is relatively simple, weighs less than typical prior art mechanisms, and which in a preferred embodiment reduces strand misalignment problems. In its broadest aspect the invention provides, for a continuous casting machine, a mold reciprocating mechanism comprising:

a. a piston including a mold sleeve therein, said mold sleeve being adapted to receive a mold cartridge for metal;

b. support means for supporting said mold cartridge within said mold sleeve;

c. a cylinder encircling said piston between the ends of said piston with said piston projecting from both ends of said cylinder, said piston and cylinder being connected for reciprocating motion of said piston relative to said 7 cylinder; (1, fluid entry and exit means in said cylinder for directing 7 pressure fluid into and out of said cylinder to drive said 1 piston with said reciprocating motion;

e. and flexible conduit means connected to said piston for admitting cooling fluid thereto to cool said mold cartridge.

The invention in another of its aspects also provides control means which adjusts the speed of reciprocation as the strand withdrawal rate varies. In typical continuous casting machines, the operator will frequently vary the speed with which the withdrawal machinery withdraws the cast metal strand from the mold cartridge, to keep the liquid level in the mold cartridge, to keep the liquid level in the mold cartridge constant during variations in flow into the mold. The speed at which the mold cartridge moves in the direction of strand withdrawal (forward movement) should ideally always be kept about to percent higher than the strand withdrawal speed. Accordingly, the invention in another of its aspects provides sensing means responsive to the rate at which the strand is being withdrawn, and means responsive to the signal produced by the sensing means to control the rate of fluid flow into the cylinder of the mold reciprocator thus to vary the speed at which the piston travels during reciprocation.

The invention is also concerned with the question of adjustments necessary when it is desired to change the size of the strand being cast, e.g. from a 4 inch square to a 5 inch square. In continuous casting machines there is usually a roller apron spaced from the mild or cartridge outlet to receive and guide the strand, and adjustments must be made to rollers on both sides of the roller apron each time the strand size is changed. In the invention in one of its aspects, the mold cylinder is mounted on a slidable frame which can be slid to align one side of the billet with the roller apron, so that fewer parts of the roller apron require adjustment.

Further objects and advantages of the invention will appear from the following disclosure, taken together with the accompanying drawings, in which:

FIG. 1 is a generalized sectional view of a mold reciprocating structure according to the invention, with some details of the piston and cylinder structures omitted for simplicity, and with the face rollers'and spray chambers omitted;

FIG. 2 is a view along lines II-II of FIG. 1;

FIG. 3 is a detailed section of the apparatus of FIG. 1, taken along lines IIIIII of FIG. 1; 1

FIG. 4 is a sectional view showing pins used to locate the mold cartridge of the FIGS. 1 and 2 structure;

FIG. 5 is a diagrammatic side view showing a roller apron and withdrawal machine for use with the mold reciprocating I structure of FIGS. 1 to 3;

FIG. 6 is a schematic showing a control system to control the speed of reciprocation of the structure of FIGS. 1 to 3; and

FIG. 7 is a schematic showing a modification of the control system of FIG. 6.

Reference is first made to FIGS. 1 and 2, which indicate in slightly simplified form the main outlines of a mold reciprocation mechanism according to the present invention. The mechanism includes a frame generally indicated at 2 slidably mounted on support beams 4. The frame 2 can be slid back and forth on the beams 4 by means of bolts 6 projecting from the ends of the frame 2 through cross pieces 8 secured to the beams 4. Nuts 10 are'used to retain the frame 2 in desired position.

The frame 2 contains four upstanding columns 12, one near each corner of the frame. Each column carries at its top a bolt, lock nut and leveling screw combination 14. The bolts 14 serve to hold a support plate 16 (see FIG. 3) to which is secured a circular cylinder 18. Located within the cylinder 18 is a circular piston 20 having a circular outer wall 22 and an inner wall 24, the inner wall 24 being square in cross section. The inner wall 24 may be termed a mold sleeve. Located within the mold sleeve 24 is a mold cartridge 26 (also of square cross section) made of high thermal conductivity material such as copper. Molten metal is poured into the top of the mold cartridge (typically by a tundish not shown), is cooled during its stay in the mold cartridge, and is then withdrawn as a square strand 28 having a solidified skin.

As shown in FIG. 3, the cylinder 18 encircles the central part of the piston 20 and consists of a central wall 30, a pair of gland rings 32 (one bolted to each end of the central wall 30), and a pair of V-packings 34 to seal the space 36 between the piston and cylinder. The central cylinder wall contains inlet and outlet ports 38 (FIG. 2) for hydraulic fluid. These ports would not normally appear in FIG. 3, but their level is indicated in dotted lines in FIG. 3 for added clarity.

The piston outer wall 22 includes a central tubular wall 40 having a central flange 41 carrying piston rings 42 to divide space 36 into two chambers for pressure fluid. The wall $0 is connected at its top to a flange 43 by a retaining ring 44. The flange 43 is connected by bolts 46 spaced around its periphery to upper and lower clamping rings or plates 43, 50. The upper clamping plate 48 contains a recess 52 in its lower surface to accommodate a retaining plate 54 for the mold cartridge 26. In addition, the inner periphery of the upper clamping plate 48 is spaced by a slight clearance from the mold cartridge 26 which it encircles (e.g. by one-thirty seconds inch) to allow slight lateral movement of the mold cartridge for a reason to be explained.

The retaining plate 54 is circular in outline as viewed from above, with a square central hole for the mold cartridge, and fits into a groove 56 in the mold cartridge to support the latter. The retaining plate 54 may be formed as two halves so that it can be fitted into the groove 56in the mold cartridge. It will be noted that there is again a small clearance (e.g. one-thirty seconds inch) between the outer periphery of the retaining plate 54 and the edge of the recess 52 in the upper clamping plate, so as to permit slight lateral movement of the retaining plate 54 and mold cartridge 26. This helps to reduce misalignment of the mold cartridge, as will be explained.

Located below the retaining plate 54 are an O-ring retainer plate 58 and a sealing ring 60. Plate 58 and ring 60 are located in a recess 62 in the upper surface of the lower clamping ring 50. Located between plate 58 and ring 60 are two O-rings 64. This combination serves as an upper seal for the cooling water in the interior space 66 in the piston, the O-ring retainer plate 60 acting as a seal against the mold cartridge 26 and the sealing ring acting as a seal against the lower clamp ring 50. Again, both plates 58, 60 are about one-thirty seconds inch smaller in diameter than the recess 62 in the lower clamping ring 50, to permit slight lateral movement of the mold cartridge 26.

The construction at the bottom of the piston is similar to that at the top, except that no retaining plate similar to plate 54 is provided at the bottom and primed reference numerals indicate parts at the bottom of the piston corresponding to parts at the top. Since the mold cartridge is suspended only at one location, it can expand axially when heated. The clearance (indicated at 68) between the outer surface of the mold cartridge 26 and the mold sleeve 24 is maintained by threaded pins 70 (best shown in FIG. 4) which turn through nuts 72 welded to the mold sleeve and are locked in place by nuts 74. There are eight columns of pins 70, two columns straddling the center of each of the four faces of the mold cartridge, typically with three pins in each column. The pins permit slight lateral movement of the mold cartridge for alignment purposes.

The piston 20 is supplied with cooling water (to cool the mold cartridge 26) through flexible hoses 76 are each fitted with directional check valves 80. Two hoses are provided for each of the inlet and outlet in case one hose should rupture during use. The flexible portion of the hose will withstand reciprocation of the piston since the maximum travel of the piston does not usually exceed 2 inches (a typical stroke for the piston is to 1% inches).

The hoses 76, 78 enter and leave the piston through inlet couplings 82 leading into inlet ports 84, and outlet couplings 86 leading from outlet ports 88. The ports would nor normally appear in FIG. 3, but they are indicated in dotted lines to show their elevation.

When water from the inlet hoses enters the piston 20, it fills the space 66 (FIG. 3) between the piston outer central wall 40 and the mold sleeve 24, up to the level of a stop plate 90. The water also travels through ports 92 at the bottom of the mold sleeve and upwardly at high velocity through the narrow clearance 68 between the mold sleeve 24 and the mold cartridge 26. This water performs the bulk of the mold cooling, and then exits through ports 96 at the top of the mold sleeve and enters the outlet ports 88. The water in the central space 66 ensures that the hydraulic fluid used to move the piston does not overheat.

During casting, lubrication for the strand is provided via four channels 98 (FIG. 3) in the upper clamping ring, one leading toward each corner of the mold cartridge. The channels 98 lead into a groove 100 encircling the top of the mold cartridge. Lubricant (usually rapeseed oil) pumped into the channels 98 overflows the top of the groove and travels through a narrow clearance 102 between the upper clamping plate 48 and a cover plate 104, and then travels down between the sides of the mold cartridge 26 and the molten metal. There the lubricant is carbonized and helps prevent the metal from sticking to the mold.

The overaLl piston assembly, and also the fixed frame 2, is protected from molten metal splash by a mold cove 105 resting on the upper clamping plate 48 and integral with the cover plate 104. Further removable cover plates 106 assist in protecting against splash.

When the metal strand leaves the mold cartridge, it enters a face roller assembly indicated in dotted lines at 108 (FIGS. 2, 3). The face roller assembly is fixed to the lowermost clamping plate 48 by screws 110 and contains opposed pairs of face rollers 112, 114 and 116, to guide the strand as it emerges from the mold cartridge.

By the time the strand reaches the bottom of the mold cartridge 26, its skin will have shrunk away from the mold cartridge to provide about l/64th-inch clearance all around. The face rollers are spaced apart an appropriate distance so that they will contact the strand skin as the strand emerges. In prior art machines, it was necessary to ensure that the face rollers assembly was precisely concentric with the mold cartridge, but with the construction shown, less care is needed because the mold cartridge can move horizontally one-thirty second inch in any direction and therefore it can align itself. The pressure of the clamping rings on plates 54, 58, 60 at the top, and on the corresponding bottom plates, is made low enough to permit this sliding movement.

As the strand emerges from the face roller assembly 108, it enters a spray chamber where it is sprayed with cooling water to speed its solidification. The spray chamber, which can be of any desired nature, is not illustrated in detail, but FIG. 3 shows at 118 its outlines. The beams 120 of the spray chamber rest on beams 122 connected to the columns 12.

After the strand 28 leaves the spray box, it enters a roller apron 124 FIG. 5 which guides it through a strand withdrawal machine 126. Typically the roller apron is curved to reduce the overall height of the machine. In the past, each time the strand size was changed, it was necessary to move the roller apron, but with the present invention, the frame 128 of the roller apron remains fixed. When the billet size is changed e.g. from 4 to 5 inches (by changing the mold cartridge 26), the entire mold frame 2 is moved to the right as shown in FIG. 5 by a distance equal to one-half the change in billet size. Spacer bars 129 (FIGS. 1, 2) may be provided on the bolts 6 used to move the mold frame to indicate to an operator the correct distance to move. This movement align's the left side of the mold cartridge with the left-hand rollers 130 of the roller apron. The left-hand rollers 130 are mounted on a fixed support beam 131. The right-hand rollers 132 of the roller apron (which are mounted on a fixed support beam 133) are then adjusted outwardly by a distance equal to the change in strand size. Typically, these rollers are mounted on hangers 134 adjustable in the direction of the arrows 136 by nuts, so that the rollers can be moved as required.

In the strand withdrawal machine 126, the bottom rollers 137 are fixed, and the top pressure rollers 138 are forced against the strand 28 by pistons 139 which thus allow for change of strand size.

It may be noted that in the past, it was necessary to the mold cartridge 26 accurately axially relative to the rollers of the roller apron 124. Failure to achieve good axial alignment resulted in twisting of the newly formed strand and wear of the mold cartridge, shortening mold cartridge life. In the apparatus herein described, the piston 20 is free to rotate in the cylinder 18, so that the mold cartridge and supporting mechanism will rotate to minimize stresses caused by axial misalignment. Rotation of the mold cartridge and its supporting piston is of course limited by the water and oil lines connected to the piston, but no more than about 2 of movement is normally needed to allow for axial misalignment, and the flexible hoses permit at least this much movement.

The control system which controls the speed and direction of piston movement will next be described. In continuous casting, the speed of movement of the reciprocating mold cartridge in the direction of strand withdrawal should generally be about to percent greater than the strand withdrawal speed, so that the mold will overtake the newly formed strand and heal small cracks in the strand skin. On the reverse or upward stroke, the mold cartridge speed should usually b 2 to 3 times the strand withdrawal speed. During casting, the strand withdrawal speed, i.e. the speed of operation of the strand withdrawal machine 126, will be varied by the operator so as to keep the level of molten metal in the mold fairly constant during variations in the rate of pour of metal into the mold. Therefore, the speed of reciprocation of the mold cartridge should also vary, at least for high quality steel.

It is here assumed that the drive motors of the withdrawal mechanism are hydraulic motors the speed of which is controlled by varying the setting of a variable displacement pump supplying fluid to the motors. Thus, FIG. 6 shows a stem servo controlled variable displacement pump I40 supplying oil to drive motors N2 of the strand withdrawal machine. Coupled to the stern 144 of the stern servo controlled pump (which may be e.g. VickersSperry variable displacement pump model PVB-45) by any desired linkage 146 is the shaft 148 of a dif ferential transformer 150. The position of the shaft 148 varies depending on the setting of the stem 144 of pump 140 an is thus a speed indicator.

cycles per second. The transformer 150 includes a standard two coil secondary winding, such coils being wound in opposed directions and being arranged so that when the shaft M8 is at a reference position, the outputs from the two coils cancel each other providing a zero output, and when the shaft M8 is moved, an AC output voltage results of magnitude dependent on the shaft position.

The transformer output is connected through limit switch contacts 156, 158 and through forward and reverse potentiometers 160, 162 to a servoamplifier 164 (typically a Vickers-Sperry servoamplifier model EM D 10). The limit switch contacts 156, 158 are part of limit switches 166, 168 (FIG. 1) attached to the fixed mold frame 2 and actuated by a moving actuator 170 connected to the moving piston structure (e.g. to the mold cover 105).

The signal from the forward or reverse potentiometer is matched in the servoamplifier 164 with a DC reference signal, and a pair of output signals depends on the size and polarity of the difference between the input signal and the reference signal. The output signals are fed via conductors 172 to the two coils of the torque motor 174 of a servovalve 176. The servovalve is a standard Vickers-Sperry electrohydraulic industrial servovalve series SA4-06 having an armature which turns by an amount and directiondependent on the current unbalance in the coils of the motor. The armature moves a valve spool diagrammatically indicated at 178 in a direction and by an amount and direction dependent on the current unbalance in the coils of the motor. The armature moves a valve spool diagrammatically indicated at 178 in a direction and by an amount dependent on the current unbalance to control the direction and rate of movement of the piston 20.

la operation, the system is initially set as follows. Assume that a casting speed of 100 inches per minutes is desired. The stem servo 11410 is then set at a position that will produce this withdrawal speed, moving the shaft 146 of the transformer 11% to a corresponding position. The forward potentiometer ms is then set to produce a downward speed of the piston of about 105 inches per minute, and the reverse potentiometer is set to produce an upward speed e.g. of 300 inches per minute. Variations in withdrawal speed during operation will now antomatically result in variations in the speed of travel of piston 20 during reciprocation.

If desired, the limit switches I66, 168 can be replaced by proximity switches which do not require physical contact for operation. The contacts 156, 158 will then be contacts of the proximity switches instead of being contacts of limit switches. In addition, if desired, the bottom limit switch 160 can be eliminated and replaced by a timer 180, as shown diagrammatically in FIG. 7 where primed reference numerals indicate corresponding parts. The timer resets automatically once its time is up and is connected by a conductor 182 to upper limit switch contact 156' to commence timing each time this contact is closed.

With this arrangement, when the moving actuator hits the upper limit switch 160, this closes contact 156' to start the piston moving down, and the time of downward movement is controlled by the timer. After a preset time has elapsed, the contact 158', which is now a contact of timer 180, closes momentarily and starts the piston moving up again.

The purpose of this arrangement is to provide mold stroke adjustment which varies automatically as the casting speed vaties. In continuous casting the mold stroke must be larger at high strand withdrawal speeds then at low strand withdrawal speeds. By use of the timer, together with the means already shown for varying the speed of reciprocation with strand withdrawal speed, the mold stroke will in fact vary with withdrawal speed as required. For example, assume that withdrawal speed is 115 inches per minute and that the downward reciprocating speed is 120 inches per minute. Then if the timer times for an interval of tag. one-half second, the downward stroke will be 1 inch. If the withdrawal speed is doubled, the mold downward reciprocating speed will also automatically double to 240 inches per minute, and because the timing interval is still one-half second, the stroke will double to 2 inches.

The timer can if desired be used to time travel in the upward direction instead of the downward direction, but timing of the travel in the direction of strand withdrawal is preferred.

It will be realized-that although it has been assumed that a strand of square cross section is being cast, the apparatus described can be used forstrands or billets having various cross-sectional shapes. For example, the strand can be rectangular, or I-beam shaped, or any other appropriate shape as desired. The mold cartridge 26 will be shaped accordingly, to cast the strand with the desired cross section, and the mold sleeve 24 will also normally correspond in cross section to that of the strand being cast.

We claim:

1. For a continuous casting machine, a mold reciprocating mechanism comprising:

a. a piston including a mold sleeve therein, said mold sleeve being adapted to receive a mold cartridge for metal; support means for supporting said mold cartridge within said mold sleeve; c. a cylinder encircling said piston between the ends of said piston with said piston projecting from both ends of said cylinder, said piston and cylinder being connected for reciprocating motion of said piston relative to said cylinder; fluid entry and exit means in said cylinder for directing pressure fluid into and out of said cylinder to drive said piston with said reciprocating motion; and

e. flexible conduit means connected to said piston for admitting cooling fluid thereto to cool said mold cartridge.

2. A mechanism according to claim 1 including a frame, a support plate connected to said cylinder, and levelling means connecting said support plate to said frame for levelling of said cylinder and consequently levelling of said piston and mold cartridge.

3. A mechanism according to claim 2 wherein said piston includes a tubular central outer wall, and said cylinder includes a tubular central wall encircling said piston central wall with a space therebetween for pressure fluid, said piston central wall having projecting sealing means extending therearound sliding against said cylinder central wall to form a seal therearound and divide said space into a pair of chambers, said piston being rotatable axially at least to a limited extent in said cylinder to reduce axial misalignment of a cast strand in said mold.

4. A mechanism according to claim 1 wherein said support means (b) includes means permitting slight lateral movement of said mold sleeve within said piston to reduce lateral strand misalignment,

5. A mechanism according to claim 1 wherein said support means (b) includes a retainer plate connected to one end of said mold cartridge, and a pair of clamping plates connected to said piston structure and clamping said retainer plate between them for limited lateral sliding movement of said retainer plate between said support plates, thus to allow slight lateral adjustment of said mold within said mold sleeve.

6. A mechanism according to claim 1 wherein said support means (b) retains said mold cartridge with the axis of said mold cartridge vertically aligned, said means (b) including at the top of said piston structure:

i. A retainer plate encircling said mold cartridge and connected thereto;

ii. a pair of sealing plates located below said retainer plate also encircling said mold cartridge;

iii. upper and lower clamping plates encircling said retaining and sealing plates and having cooperating recesses in their lower and upper surfaces respectively to accommodate said retaining and sealing plates, with a slight lateral clearance between the outer peripheries of said recesses and the other peripheries of said retaining and sealing plates to permit slight lateral movement of said mold cartridge, the clamping pressure of said clamping plates being such as to permit such lateral sliding movement, said sealing rings providing a seal against loss of said cooling water in said piston out the top of said piston structure; and

said means (b) further including at the bottom of said piston structure a pair of further sealing plates encircling said mold cartridge, and a pair of further clamping plates encircling said further sealing plates and having further cooperating recesses within which said further sealing plates are accommodated, with a slight lateral clearance between the outer peripheries of said further sealing plates to permit slight lateral movement of the bottom part of said mold cartridge, said mold cartridge being suspended only at said upper retainer ring to allow axial heat expansion of said mold cartridge.

7. A mechanism according to claim 2 including support beams for said frame, said frame being slidably mounted on said support beams, and adjustment means for moving said frame back and forth on said support beams.

8. A mechanism according to claim 7 including a roller apron below said support beams to receive a strand emerging from said mold cartridge, said roller apron having a pair of fixed side member, one on each side of said strand, each said side members, one on each side of said strand, each said side member carrying rollers to guide said strand, the rollers on one of said side members being fixed and means on said other side member mounting the rollers thereon for lateral adjustment towards and away from the path of travel of said strand, thus permitting change of strand size by lateral adjustment of said frame and of said rollers on said other side member.

9. A mechanism according to claim 1 and for use with a continuous casting machine of the type including variable speed drive means for withdrawing said strand from said mold cartridge at a speed which can be varied, said mechanism including variable signal means responsive to the condition of said withdrawal drive means to produce a signal proportional to the withdrawal speed of said strand, valve means operative to control the rate of flow and direction of pressure fluid into said cylinder to control the direction of movement of said piston and the speed of movement of said piston, and means connected between said signal means and said valve means for operating said valve means responsive to said signal to control the direction and rate of flow of fluid into said cylinder, said last mentioned means including switching elements responsive to movement of said piston structure to cyclically operate said valve means to reverse the movement of said piston structure.

10. A mechanism according to claim 2 and for use with a continuous casting machine of the type including variable speed drive means for withdrawing said strand from said mold cartridge at a speed which can be varied, said mechanism further including:

1. fluid control means operable to control the rate and direction of pressure flow into said cylinder to control the direction and speed of travel of said piston;

2. means coupled to said fluid control means and responsive to the speed of withdrawal of said strand for operating said fluid control means to vary the speed of travel of said piston proportionally with changes in said strand withdrawal speed;

3. said cylinder and frame including cooperating switching means responsive to a predetermined extreme position of said cylinder to operate said fluid control means to reverse the direction of travel of said piston; and

4. timing means coupled to said fluid controlmeans and responsive to said reversal of travel of said piston to permit travel of said piston following said reversal for a preset interval and then for again reversing said direction of travel of said piston, said timing means being self resetting to commence retiming following a still further reversal of travel of said piston by said switching means.

11. A mechanism according to claim 10 wherein said switching means is positioned to reverse the direction of travel of said piston from travel opposite the direction of strand withdrawal to travel in the direction of strand withdrawal. 

1. For a continuous casting machine, a mold reciprocating mechanism comprising: a. a piston including a mold sleeve therein, said mold sleeve being adapted to receive a mold cartridge for metal; b. support means for supporting said mold cartridge within said mold sleeve; c. a cylinder encircling said piston between the ends of said piston with said piston projecting from both ends of said cylinder, said piston and cylinder being connected for reciprocating motion of said piston relative to said cylinder; d. fluid entry and exit means in said cylinder for directing pressure fluid into and out of said cylinder to drive said piston with said reciprocating motion; and e. flexible conduit means connected to said piston for admitting cooling fluid thereto to cool said mold cartridge.
 2. A mechanism according to claim 1 including a frame, a support plate connected to said cylinder, and levelling means connecting said support plate to said frame for levelling of said cylinder and consequently levelling of said piston and mold cartridge.
 2. means coupled to said fluid control means and responsive to the speed of withdrawal of said strand for operating said fluid control means to vary the speed of travel of said piston proportionally with changes in said strand withdrawal speed;
 3. said cylinder and frame including cooperating switching means responsive to a predetermined extreme position of said cylinder to operate said fluid control means to reverse the direction of travel of said piston; and
 3. A mechanism according to claim 2 wherein said piston includes a tubular central outer wall, and said cylinder includes a tubular central wall encircling said piston central wall with a space therebetween for pressure fluid, said piston central wall having projecting sealing means extending therearound sliding against said cylinder central wall to form a seal therearound and divide said space into a pair of chambers, said piston being rotatable axially at least to a limited extent in said cylinder to reduce axial misalignment of a cast strand in said mold.
 4. A mechanism according to claim 1 wherein said support means (b) includes means permitting slight lateral movement of said mold sleeve within said piston to reduce lateral strand misalignment.
 4. timing means coupled to said fluid control means and responsIve to said reversal of travel of said piston to permit travel of said piston following said reversal for a preset interval and then for again reversing said direction of travel of said piston, said timing means being self resetting to commence retiming following a still further reversal of travel of said piston by said switching means.
 5. A mechanism according to claim 1 wherein said support means (b) includes a retainer plate connected to one end of said mold cartridge, and a pair of clamping plates connected to said piston structure and clamping said retainer plate between them for limited lateral sliding movement of said retainer plate between said support plates, thus to allow slight lateral adjustment of said mold within said mold sleeve.
 6. A mechanism according to claim 1 wherein said support means (b) retains said mold cartridge with the axis of said mold cartridge vertically aligned, said means (b) including at the top of said piston structure: i. A retainer plate encircling said mold cartridge and connected thereto; ii. a pair of sealing plates located below said retainer plate also encircling said mold cartridge; iii. upper and lower clamping pLates encircling said retaining and sealing plates and having cooperating recesses in their lower and upper surfaces respectively to accommodate said retaining and sealing plates, with a slight lateral clearance between the outer peripheries of said recesses and the other peripheries of said retaining and sealing plates to permit slight lateral movement of said mold cartridge, the clamping pressure of said clamping plates being such as to permit such lateral sliding movement, said sealing rings providing a seal against loss of said cooling water in said piston out the top of said piston structure; and said means (b) further including at the bottom of said piston structure a pair of further sealing plates encircling said mold cartridge, and a pair of further clamping plates encircling said further sealing plates and having further cooperating recesses within which said further sealing plates are accommodated, with a slight lateral clearance between the outer peripheries of said further sealing plates to permit slight lateral movement of the bottom part of said mold cartridge, said mold cartridge being suspended only at said upper retainer ring to allow axial heat expansion of said mold cartridge.
 7. A mechanism according to claim 2 including support beams for said frame, said frame being slidably mounted on said support beams, and adjustment means for moving said frame back and forth on said support beams.
 8. A mechanism according to claim 7 including a roller apron below said support beams to receive a strand emerging from said mold cartridge, said roller apron having a pair of fixed side member, one on each side of said strand, each said side members, one on each side of said strand, each said side member carrying rollers to guide said strand, the rollers on one of said side members being fixed and means on said other side member mounting the rollers thereon for lateral adjustment towards and away from the path of travel of said strand, thus permitting change of strand size by lateral adjustment of said frame and of said rollers on said other side member.
 9. A mechanism according to claim 1 and for use with a continuous casting machine of the type including variable speed drive means for withdrawing said strand from said mold cartridge at a speed which can be varied, said mechanism including variable signal means responsive to the condition of said withdrawal drive means to produce a signal proportional to the withdrawal speed of said strand, valve means operative to control the rate of flow and direction of pressure fluid into said cylinder to control the direction of movement of said piston and the speed of movement of said piston, and means connected between said signal means and said valve means for operating said valve means responsive to said signal to control the direction and rate of flow of fluid into said cylinder, said last mentioned means including switching elements responsive to movement of said piston structure to cyclically operate said valve means to reverse the movement of said piston structure.
 10. A mechanism according to claim 2 and for use with a continuous casting machine of the type including variable speed drive means for withdrawing said strand from said mold cartridge at a speed which can be varied, said mechanism further including:
 11. A mechanism according to claim 10 wherein said switching means is positioned to reverse the direction of travel of said piston from travel opposite the direction of strand withdrawal to travel in the direction of strand withdrawal. 